So you're suggesting that Apple could have made two distinct and incompatible (so far as cellular networking goes) products.
Why is this so radical, exactly? There is a CDMA Palm Pre for Sprint and Verizon, and a GSM Palm Pre for AT&T. I don't follow the mobile product landscape too closely, but I'm sure there are others. The phones don't have to interoperate with each other, just the networks they're on. It's simple, if you want access to more subscribers, you make a CDMA variant of your phone. Apple decided to do the exclusive thing for 5 years or whatever. Nobody forced them to.
The US product further unable to be taken out of the country because it would fail to work anywhere else.
There are plenty of people who choose a phone that doesn't work overseas, myself included. I'd rather deal with using a prepaid phone overseas than to be a slave to AT&T.